In the process of making paper wherein a fiber furnish is introduced at the inlet side of a conventional papermaking machine, such as a Fourdrinier machine, it has become the accepted procedure to add polymeric materials to the furnish in order to improve the drainage rate of the furnish on the machine. Generally, it was preferred to utilize high molecular weight materials for this purpose because the higher molecular weight materials have proven to be the more successful flocculants in other flocculation procedures. U.S. Pat. No. 3,323,979 is exemplary of the prior art in this area. This patent teaches the use of Mannich acrylamide polymers having molecular weights over 1,000,000 to increase the drainage rate of the furnish when preparing paper.
Papermaking machines of the Fourdrinier type generally contain three specific zones wherein water is removed from the deposited web of fibers supported on the wire. The first water removal zone is where water is removed by gravity. It is positioned immediately subsequent to the slice of the headbox. The next water-removal zone is the low vacuum drainage zone where a low vacuum is generated by the rapid motion of the wire of the Fourdrinier table over the foils and table rolls thus drawing water from the deposited wet web. The third and final dewatering zone between the first flat boxes and the couch roll is a high vacuum zone where the water is squeezed from within the fiber flocs by the negative vacuum pressure. The wet web at consistencies reading up to 25% leaves the Fourdrinier table wire at this point and is transferred to the press section of the paper machine. The web then moves to the driers or drying cylinders section where the remaining water is completely removed by evaporation. The energy required to operate the driers is the most expensive step in water removal from the wet web while dewatering on the wire of the Fourdrinier table is the least.
Attempts to reduce the amount of water present in the paper web introduced into the driers have been ongoing, and continue to be ongoing, since the costs of energy continue to rise. Therefore, if the removal of water from the wet paper web entering the driers in the papermaking process could be reduced, a long-felt need in the industry would be satisfied.